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Talk of “global cooling” based on bogus statistics

The Associated Press sent out temperature data to a set of statisticians …

There's an inevitable problem with trying to find trends in data that is subject to a great deal of random variability: unless the most recent point was a record high, it will always look like there's a downward trend. We're currently seeing that happen with the global temperature record, where the warmest year ever recorded, 1998, is receding into the past. As a result, reports of "global cooling" are appearing in the popular press, and smaller percentages of the US public are confident that the globe is warming. Unfortunately, all of this seems to be a misdirection; the Associated Press has performed a statistical sanity check on the claims of global cooling, and found that there's little to them.

As the AP report notes, the cries of global cooling have become increasingly obvious, with the phrase appearing on the cover of the new book Super Freakonnomics and the BBC asking "What happened to global warming?"

But, as we noted in February, the recent drop in temperatures has been so small that 2008 was still the 10th warmest on record. Other recent years were equally warm or warmer, while the hottest year on record, 1998, was unusually warm compared to the surrounding years. In fact, if you started tracking trends in either 1997 or 1999, you saw a general increase in global temperatures.

The AP went beyond this analysis by sending out temperature data to four statisticians, without informing them what the data represented, and asked them to identify any trends in the data. Apparently, none of them saw any sign of global cooling. All of them detected the upward trend that is apparent when periods longer than a decade are examined, while the ups-and-downs of the last decade appear similar to the statistical noise that occurs in other decades within the data set. One of the statisticians is even quoted as saying that seeing a downward trend in recent years involves "people coming at the data with preconceived notions."

Statistically valid or not, the high profile of the sites where claims of global cooling are being given credence appears to be weighing in with the public. Last week, the Pew Research Center released the results of a poll of 1,500 US adults, who were asked about climate change. Over the past year, acceptance of the data showing that the Earth has warmed plunged, dropping from 71 percent of respondents to 57 percent. Far fewer accept the verdict of most scientists, namely that human influences are the primary driver of recent climate changes. Here, only 36 percent of the public agreed.

Although the partisan divide remained—Republicans are far less likely to accept the science—the decline occurred across all party affiliations, and was most dramatic among independents.

The poll also registered the typical confusion that the US public experiences when faced with scientific matters. About half of those surveyed either don't think the evidence for warming is solid, or think it's the result of natural variation. But a third of those still consider it a serious problem.

It would be tempting to view the recent drop in the acceptance of climate change as an indication that the public is losing its taste for the cap-and-trade legislation and negotiations for a binding international treaty that are leading up to the UN's Copenhagen meeting on carbon emissions limits. But the poll provides little evidence of that. Half of the respondents favored limits on carbon emissions, including 31 percent of those who think that there's no solid evidence of global warming. That doesn't necessarily mean they favor the current cap-and-trade legislation, however, as about half admitted they knew nothing about it.

An even higher percentage (55 percent) favors joining in an international agreement to limit carbon emissions, with another third saying we should set our own limits.

So, it appears that statistically bogus arguments remain popular with those who write about climate change for popular audiences, and that may be contributing to a general drop in the acceptance of the evidence and conclusions of the scientific community. But, so far at least, the plunging acceptance levels haven't translated into a backlash against policy initiatives.

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